Bug 1400148 - Don't use -1 to represent an unset nsCursor. r=karlt.

Because UBSan complains about casting -1:

> runtime error: load of value 4294967295, which is not a valid value for type 'nsCursor'

--HG--
extra : rebase_source : 037a96700228ea0d427afa7c25c40490c701cdc4

dom/ipc/TabParent.cpp

@@ -164,7 +164,7 @@ TabParent::TabParent(nsIContentParent* aManager,
   , mInitedByParent(false)
   , mTabId(aTabId)
   , mCreatingWindow(false)
-  , mCursor(nsCursor(-1))
+  , mCursor(eCursorInvalid)
   , mTabSetsCursor(false)
   , mHasContentOpener(false)
 #ifdef DEBUG
@@ -1131,7 +1131,7 @@ TabParent::SendRealMouseEvent(WidgetMouseEvent& aEvent)
       if (mCustomCursor) {
         widget->SetCursor(mCustomCursor,
                           mCustomCursorHotspotX, mCustomCursorHotspotY);
-      } else if (mCursor != nsCursor(-1)) {
+      } else if (mCursor != eCursorInvalid) {
         widget->SetCursor(mCursor);
       }
     } else if (eMouseExitFromWidget == aEvent.mMessage) {
@@ -1787,7 +1787,7 @@ TabParent::RecvSetCustomCursor(const nsCString& aCursorData,
                                const uint32_t& aHotspotY,
                                const bool& aForce)
 {
-  mCursor = nsCursor(-1);
+  mCursor = eCursorInvalid;
 
   nsCOMPtr<nsIWidget> widget = GetWidget();
   if (widget) {

widget/PuppetWidget.cpp

@@ -1012,7 +1012,7 @@ PuppetWidget::SetCursor(imgIContainer* aCursor,
     return NS_ERROR_FAILURE;
   }
 
-  mCursor = nsCursor(-1);
+  mCursor = eCursorInvalid;
   mCustomCursor = aCursor;
   mCursorHotspotX = aHotspotX;
   mCursorHotspotY = aHotspotY;

widget/gtk/nsWindow.cpp

@@ -1623,7 +1623,7 @@ nsWindow::SetCursor(imgIContainer* aCursor,
         return window->SetCursor(aCursor, aHotspotX, aHotspotY);
     }
 
-    mCursor = nsCursor(-1);
+    mCursor = eCursorInvalid;
 
     // Get the image's current frame
     GdkPixbuf* pixbuf = nsImageToPixbuf::ImageToPixbuf(aCursor);

widget/nsIWidget.h

@@ -211,8 +211,12 @@ enum nsCursor {   ///(normal cursor,       usually rendered as an arrow)
                 eCursor_ns_resize,
                 eCursor_ew_resize,
                 eCursor_none,
-                // This one better be the last one in this list.
-                eCursorCount
+                // This one is used for array sizing, and so better be the last
+                // one in this list...
+                eCursorCount,
+
+                // ...except for this one.
+                eCursorInvalid = eCursorCount + 1
                 };
 
 enum nsTopLevelWidgetZPlacement { // for PlaceBehind()

widget/windows/nsWindow.cpp

@@ -3020,7 +3020,7 @@ nsWindow::SetCursor(imgIContainer* aCursor,
   rv = nsWindowGfx::CreateIcon(aCursor, true, aHotspotX, aHotspotY, size, &cursor);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  mCursor = nsCursor(-1);
+  mCursor = eCursorInvalid;
   ::SetCursor(cursor);
 
   NS_IF_RELEASE(sCursorImgContainer);
@@ -7179,7 +7179,7 @@ void nsWindow::OnDestroy()
   }
 
   // Destroy any custom cursor resources.
-  if (mCursor == -1)
+  if (mCursor == eCursorInvalid)
     SetCursor(eCursor_standard);
 
   if (mCompositorWidgetDelegate) {